Comments on: The “Canonical” Varve Thickness Serieshttp://climateaudit.org/2013/12/04/the-canonical-varve-thickness-series/
by Steve McIntyreSun, 02 Aug 2015 16:57:45 +0000hourly1http://wordpress.com/By: Hector Pascalhttp://climateaudit.org/2013/12/04/the-canonical-varve-thickness-series/#comment-455472
Tue, 10 Dec 2013 08:32:23 +0000http://climateaudit.org/?p=18676#comment-455472Thanks Geoff. I didn’t mean to imply you were endorsing anything, simply making a more general point that it’s easy to fall into traps.

I know for certain that anyone who qualifed with a geology degree in Western Australia between about 1975 and 1995, could have done so without ever seeing any sedimentary rocks, either in the field or in hand specimen. If said geo was working with a mental model “laminated sediments = low energy environment”, then they may not have been looking for sedimentary structures. As the mineralogy is massive chert +- Fe, these features may be quite subtle.

I’m intrigued by your reference to colloidal phases. There can be no doubt that these chemical sediments behave as particles, otherwise they would not develop cross bedding. Perhaps I should consult a geochemist. I’ll bring my long handled spoon when I go to sup.

]]>By: j fergusonhttp://climateaudit.org/2013/12/04/the-canonical-varve-thickness-series/#comment-455116
Sun, 08 Dec 2013 12:20:36 +0000http://climateaudit.org/?p=18676#comment-455116Bottom Feeders?
]]>By: Geoff Sherringtonhttp://climateaudit.org/2013/12/04/the-canonical-varve-thickness-series/#comment-455105
Sun, 08 Dec 2013 11:00:34 +0000http://climateaudit.org/?p=18676#comment-455105Hector,
I was not endorsing a deposition mechanism, merely quoting some papers that might lead into further relevant reading. The main point is that there remains a good deal of scientific uncertainty in sedimentology; and while interpretative uncertainty exists, it is not safe to do some types of statistics because you do not necessarily know which variables need to be quantified and included.
Our team was strong on colloidal phases in sedimentary rock formation – I have not seen a mention of this possible mechanism in the papers referred to above, so that might serve as an example of ignoring a variable or a process that might?? be part of the required analysis.
]]>By: Hector Pascalhttp://climateaudit.org/2013/12/04/the-canonical-varve-thickness-series/#comment-455055
Sun, 08 Dec 2013 06:11:48 +0000http://climateaudit.org/?p=18676#comment-455055Thanks for the link Geoff, I enjoyed reading that. I’ve spent a lot of time doing fieldwork in the Mt Brockman area. I will take issue with this:

The common fine lamination (and/or microbanding) as well as the lack of detrital components in most BIFs suggest that such are the result of deposition, below wave base, in the deeper parts of ocean basins.

BIFs of the Hamersley Range were deposited on continental crust, and according to my knowledge of plate tectonics, continental crust doesn’t floor deep ocean basins. I have also identified to my satisfaction, plenty of ripples and large scale cross-bedding structures in BIFs. These indicate the influence of waves as well as significant currents on BIF sediments. Sedimentary structures apart from lamination may not be described in the literature, but that doesn’t mean they aren’t there. I suspect that most of the descriptive work has been done by hard-rockers who weren’t looking for and weren’t qualified to recognise them.

Also, the BIF literature is completely wrong in another area. The standard evolution goes: deposition -> compaction -> lithification -> deformation. In fact, some BIFs are full of soft sediment deformation structures (boudinage) and their aspect ratios indicate minimal compaction. A more correct evolution is: deposition -> deformation -> lithification. Compaction and D1 go straight out of the window. Not to criticise hard-rockers, but they shouldn’t stray into areas outside their competence. That’s why I stay away from maths and stats.

Unless one is a specialist in sedimentary geology, perhaps even a specialist in geological pattern matching, it is naïve to make correlations between patterns and depositional history within modern sediments. One might say that we can observe the present conditions of deposition to our advantage and hence infer more than we can from old rocks, which is in part correct. The other part is that some parameters can change in the time between the deposition we observe today and those that are eventually recorded when the sediments are lithified to a long-term constancy.

As a specialist in sedimentary geology (aka sedimentologist), I was tempted by your comment to dip into my copy of Reading (ed) Sedimentary Environments. There is a chapter on lakes, as well as a section on glaciolacustrine environments. Lakes are completely outside my area of expertise.

Paraphrasing glaciolacustrine environments.

Glacier-fed lakes are divided into ice-contact lakes and distal (non-contact) lakes fed by outwash streams. The main factors that affect physical processes and sedimentation are proximity to the ice, thermal stratification of lake water, and seasonality of inflowing meltwater and ice cover. Thermal stratification is inhibited by ice contact. Contact/non-contact may evolve with time. Stratification leads to autumnal overturning of the water layers and this influences sedimentation patterns.

In lake basinal sub-environments, seasonal fluctuations are recorded as rhythmites and varves. Sediment is deposited from suspension and by density currents, turbidity currents and mass flow. A typical succession contains rhythmically laminated or varved fine sand to clay interrupted by turbidites, current rippled sand deposited by bottom-hugging flows, and massive or graded diamicton beds deposited by mass flows.

Moving on to lakes (rhythmites).

Lamination style depends on stratification regime and suspended sediment supply. Lakes may be stratified, unstratified or partly stratified and partly unstratified. Suspended sediment supply may be continuous, discontinuous, discontinuous during stratification, discontinuous during non-stratification or discontinuous during stratification and non-stratification.

I would suggest, as is the case with statisticians, this is an area that would benefit from the employment of specialists. Limnologists, for example.

]]>By: jim2http://climateaudit.org/2013/12/04/the-canonical-varve-thickness-series/#comment-454916
Sat, 07 Dec 2013 16:25:27 +0000http://climateaudit.org/?p=18676#comment-454916Speleothems are used as a proxy for temprature at a given age. Why can’t plain limestone be used for the same purpose?
]]>By: ianl8888http://climateaudit.org/2013/12/04/the-canonical-varve-thickness-series/#comment-454784
Sat, 07 Dec 2013 04:38:49 +0000http://climateaudit.org/?p=18676#comment-454784

… a geologist only by contamination

Surely you could titrate the degree of contamination, Geoff ?

I mean, being a chemist and all … :)

]]>By: Geoff Sherringtonhttp://climateaudit.org/2013/12/04/the-canonical-varve-thickness-series/#comment-454749
Fri, 06 Dec 2013 23:46:17 +0000http://climateaudit.org/?p=18676#comment-454749Although I am a geochemist and a geologist only by contamination, it can be noted that sedimentary deposition is a major topic in geology. In some places it has special features that draw specialist studies. One such case is the Brockman Iron Formation in West Australia. There are hundreds of references to past work, an entry level one being http://ammin.geoscienceworld.org/content/90/10/1473.short
“…..microbanding is especially well developed in the Brockman Iron Formation of Western Australia, where it has been interpreted as chemical varves, or annual layers of sedimentation. BIFs ranging in age from 2.2 Ga to about 1.8 Ga…”
These BIFs are among the types of iron ores mined on a large scale and that has attracted extra study focus. Despite the study and the observation of pattern matching of fine banding over distances of hundreds of km, there are many remaining unknowns about the factors affecting deposition. The science is not settled. The cited article uses cautious prose as if more developments are expected.
Unless one is a specialist in sedimentary geology, perhaps even a specialist in geological pattern matching, it is naïve to make correlations between patterns and depositional history within modern sediments. One might say that we can observe the present conditions of deposition to our advantage and hence infer more than we can from old rocks, which is in part correct. The other part is that some parameters can change in the time between the deposition we observe today and those that are eventually recorded when the sediments are lithified to a long-term constancy. That is why geos have terms like penecontemporaneous dedolomitization, to use Nth American spelling.
One short message is that you cannot write a definitive paper when you do not know (and cannot know) some past conditions. The known and unknown unknowns appear to exert too large an influence to allow definitive statements. That is what I meant above when suggesting that one has first to establish that a useful signal can be separated from the noise. The ‘noise’ here is the unknowns, which can show themselves in data that goes up at one place and time and down at a nearby place at a similar time – as Steve has illustrated with the 5 graphs of Shi sediments. (To average these, if that was done, is schoolboy howler stuff).
Another short message is that you cannot swoop in wearing a ‘climate scientist’ seal of approval and expect to be correct.
]]>By: stevepostrelhttp://climateaudit.org/2013/12/04/the-canonical-varve-thickness-series/#comment-454743
Fri, 06 Dec 2013 23:19:08 +0000http://climateaudit.org/?p=18676#comment-454743“It is not possible to drill to the Earth’s core.”

Not all agree, although “possible” and “practical” are not the same thing.

]]>By: Kenneth Fritschhttp://climateaudit.org/2013/12/04/the-canonical-varve-thickness-series/#comment-454721
Fri, 06 Dec 2013 20:29:21 +0000http://climateaudit.org/?p=18676#comment-454721“Are you saying that much of what we see is noise?”

Those doing the reconstructions admit to that. Unfortunately their approach cannot extract a signal because selection of proxies after the fact does not allow for “subtracting out” noise – assuming that the noise is random. There may well be valid temperature proxies out there but those doing the reconstructions are so wrongheaded in approach and unwilling to do the preliminary work that finding and differentiating those proxies from the invalid ones will not be an easy task.

I suspect the field you worked in was driven by profit and loss and involved science that was “harder” than that used in constructing temperature proxies. You had the opportunity to conclusively test the validity of your methods – and without waiting years for out-of-sample test results. And profit and loss are good motivators for getting it right or at least better.